Chlorinated hydrocarbon side products

Combustion by Utilization of Chlorinated Hydrocarbon Side Products. 81... 

While ethyl chloride is one of the least toxic of all chlorinated hydrocarbons, CE is a toxic pollutant. The off-gas from the reactor is scrubbed with water in two absoiption columns. The first column is intended to recover the majority of unreacted ethanol, hydrogen chloride, and CE. The second scrubber purifies the product fiom traces of unreacted materials and acts as a back-up column in case the first scrubber is out of operation. Each scrubber contains two sieve plates and has an overall column efficiency of 65% (i.e., NTP = 1.3). Following the scrubber, ethyl chloride is finished and sold. The aqueous streams leaving the scrubbers are mixed and recycled to the reactor. A fraction of the CE recycled to the reactor is reduced to ethyl chloride. This side reaction will be called the reduction reaction. The rate of CE depletion in the reactor due to this reaction can be approximated by the following pseudo first order expression ... 

Note that the production of C is not stoichiometrically determined but that the relative amounts of B and C can be changed by varying the reaction conditions. Had C been stoichiometrically determined, as in the production of byproduct HCl when hydrocarbons are directly chlorinated, there is nothing that can be done short of very fundamental changes to the chemistry, e.g., using CIO2 rather than CI2. Philosophically, at least, this is a problem for a chemist rather than a chemical engineer. In the present example, component C is a secondary or side product such as a dichlorinated compound when... 

It is interesting that the selectivity to chlorinated hydrocarbons is rather low and constant over time, implying a highly selective side reaction towards chlorinated products. 

In conclusion, our exposure pattern to pesticides is significantly different than before the appearance of Silent Spring. We do not use chlorinated hydrocarbons any longer, and our only exposure to them is as very low residues in primarily certain animal products, not on produce. We do not spray them on crops. Only a few percent of the produce consumed by Americans contain minute amount of pesticides. It is time that people appreciate the real risks and leave DDT to the historians. Yet from another perspective, we must remember both sides of the DDT issue when we design realistic regulations for the next century. Benefits must be a factor, especially when deciding to remove an existing compound from the market. What are the consequences ... 

The best known of these is the ozonation of tertiary amines to amine oxides (II) (i). Henbest and Stratford (11) and Shulman (17) have shown that competing with this is an ozone attack on the alpha position of an alkyl side chain to produce various decomposition products of III. Henbest (11) showed that amine oxide formation is favored in chloroform and methanol, while side chain oxidation is predominant in hydrocarbon solvents. Also of considerable interest are the reported conversions, during ozonation, of phenylenediamines to Wursters salts (VII) (8, 14), of liquid ammonia to ammonium ozonate (VA) at a low temperature 18), and of amines to amine hydrochlorides (VB) in chlorinated hydrocarbon solvents 17, 19), Finally, an early report states that azobenzene and quinone are obtained upon ozonation of aniline (15). 

For removing water floating on a chlorinated hydrocarbon bottom layer, two or three drain valves at easily accessible positions should be provided. The valves should be fitted close to the tank sides to avoid the danger of the drain lines freezing up. Product tanks should be fitted with pressure-vacuum valves and with self-closing dip and sample hatches. 

This electrochemical process is also the major industrial route for sodium hydroxide production, so essentially the only side product from this initial reaction is hydrogen gas, which is later converted to water. Once the ethylene is produced from the crude hydrocarbons, it is reacted with chlorine gas ... 

Olah151 and later Messina152 found that PCI5 is a highly effective catalyst for the free-radical side-chain chlorination of arylalkanes. Chlorination in hydrocarbon or chlorinated solvents or without solvent at room temperature yields a monochlo-rinated products with high selectivity. When the reaction was carried out in polar solvents such as nitromethane and nitrobenzene, only ring chlorination occurred. 

Elimination of carbon dioxide from carboxyl, water from alcoholic hydroxyl, carboxylic acid from alkanoate, and hydrogen chloride from chlorine side groups or chain ends are typical thermal decomposition reactions in the temperature range 250-350°C. Hydrogen chloride is an important product of poly(vinyl chloride) because every second carbon atom of the hydrocarbon polymer chain is chlorine substituted. But hydroxyl, alkanoate and free carboxylic acid groups normally occur only at the ends of the macromolecular chains in customary plastics, thus the contribution of their elimination to the volatile pyrolysis products is negligible. 

Under the preparation of brombenzene it has already been mentioned that by the action of chlorine or bromine on aromatic hydrocarbons containing aliphatic side-chains, different products are formed,... 

I4 Chlorinations of hydrocarbons are notorious for their undesirable side reactions, where the desired products are further chlorinated to hi- or trisubstitutions. You are on a researeh team that is assigned to examine the operating mode of a chlorination reactor. The following homogeneous, gas-phase reactions take place in file reactor ... 

Few reactions of CIO2 with hydrocarbons have been reported except under conditions very far removed from water treatment practice. Saturated alkanes and alkyl side chains appear almost inert in its presence except where unusually stable radicals may result (benzylic hydrocarbons, e. g.). In these cases, typical products of autooxidation (see Chapter 4) have been isolated, probably by attack of O2 on intermediate free radicals formed by electron transfer (Ozawa and Kwan, 1984 Rav-Acha and Choshen, 1987 Merenyi et al., 1988) or (less likely) hydrogen atom abstraction (Chen et al., 1982). A few polycyclic hydrocarbons have been shown to be partially converted to chlorinated derivatives and quinones by CIO2 (Thielemann, 1972a Taymaz et al., 1979). 

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